Gamma-aminobutyric acid facilitates the simultaneous production of biomass, astaxanthin and lipids in Haematococcus pluvialis under salinity and high-light stress conditions

•GABA treatment promoted astaxanthin and lipids production under abiotic stress.•GABA application upregulated carotenogenesis and lipogenesis.•Cellular GABA alleviated oxidative stress caused by abiotic stress in H. pluvialis. The effects of γ-aminobutyric acid (GABA) on the biomass and astaxanthin and lipids production in Haematococcus pluvialis under combined salinity stress and high-light stresses were investigated. The results showed that the highest biomass (1.65 g L−1), astaxanthin production (3.86 mg L−1 d−1) and lipids content (55.11%) in H. pluvialis LUGU were observed under the 0.25 mM GABA treatment. Moreover, compared with salinity and high-light stress, GABA treatment also increased the transcript levels of biosynthesis genes, the contents of endogenous GABA and carbohydrates but decreased reactive oxygen species (ROS) levels. Further evidence revealed that intracellular GABA could regulate cell growth, astaxanthin production and lipids synthesis by mediating carotenogenesis, lipogenesis and ROS signalling. Collectively, this study provides a combined strategy for promoting the coproduction of astaxanthin and lipids and sheds light on the regulatory mechanism through which GABA affects cell growth, astaxanthin production and lipids biosynthesis in H. pluvialis under unfavourable conditions.